Drive hub for planet pinion carrier freeness check

ABSTRACT

An assembly includes a sun gear that includes a external gear teeth and internal axial spline teeth, a drive hub including a first sleeve portion formed with lateral holes, and insert assemblies, each insert assembly including a sleeve located in one of the holes and secured to the first sleeve portion, a plunger located in the sleeve for displacement along the sleeve, and a spring urging the plunger laterally outward toward engagement with the spline teeth.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to an apparatus for transmitting torqueto the sun gear of a planetary gear unit during a freeness check using adrive hub having ball plunger.

2. Description of the Prior Art

A planetary gear unit of an automatic transmission for an automotivevehicle includes a sun gear formed with a series of splines, a ringgear, and a planet pinion carrier supporting planet pinions, whichcontinually mesh with the ring gear and sun gear.

Each planet pinion carrier assembly is tested after assembly forfreeness, i.e., the ability to rotate without frictional restraint dueto contact with other components. This testing requires rotating thegears and pinions of the planetary gear unit by rotatably driving thesun gear with a drive hub.

Conventionally the drive hub experiences significant wear on the frontedges of splines as it makes initial engagement into the splines of thesun gear.

It is not uncommon for the drive hub to require replacement after35,000-40,000 cycles at a high replacement cost, requiring an hour ormore of maintenance labor and production downtime.

Additionally, the machine performing the test experiences intermittentstoppages (approximately 5% of cycles) due to the drive hub not meshingconsistently with the sun gear, thus creating significant losses inproductivity.

SUMMARY OF THE INVENTION

An assembly includes a sun gear that includes a external gear teeth andinternal axial spline teeth, a rive hub including a first sleeve portionformed with lateral holes, and insert assemblies, each insert assemblyincluding a sleeve located in one of the holes and secured to the firstsleeve portion, a plunger located in the sleeve for displacement alongthe sleeve, and a spring urging the plunger laterally outward towardengagement with the spline teeth.

The assembly relies on ball plungers instead of fixed splines to providethe driving surface for turning the sun gear, thereby improvingendurance, facilitating replacement, providing protection of load cells,and reducing machine nuisance stoppages.

Replacement, and providing protection of load cells.

The scope of applicability of the preferred embodiment will becomeapparent from the following detailed description, claims and drawings.It should be understood, that the description and specific examples,although indicating preferred embodiments of the invention, are given byway of illustration only. Various changes and modifications to thedescribed embodiments and examples will become apparent to those skilledin the art.

DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood by reference to thefollowing description, taken with the accompanying drawings, in which:

FIG. 1 is a cross section through a diametric plane of a drive hub;

FIG. 2 is side view of the drive hub of FIG. 1;

FIG. 3 is perspective side view of a drive hub assembly with ballplungers installed in the drive hub of FIGS. 1 and 2;

FIG. 4A is a cross section showing an insert whose plunger is aspherical ball;

FIG. 4B is a cross section showing an insert whose a plunger is a formedshaft; and

FIG. 5 is a perspective side view of the sun gear showing spline teethengageable by the ball plungers.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The drive hub 10 shown in FIGS. 1 and 2 includes a right circularcylindrical sleeve portion 12 formed with a chamfer 13, a second rightcircular cylindrical sleeve portion 14 formed with a transverse orlateral hole 16, and an intermediate right circular cylindrical sleeveportion 18 located axially between portions 12 and 14 and having alarger outside diameter than portions 12, 14. The intermediate portion18 is formed with three lateral rows of transverse through holes 20, thesurface of each hole 20 being formed with an internal screw thread.

FIGS. 3, 4A and 4B show that some of the holes 20 are filled with athreaded insert assembly 19, 19′ which includes a sleeve 22, 22′ whoseouter surface is formed with an external thread 23 that engages theinternal thread of one of the holes 20; a plunger 24, 24′ located in andsupported by the sleeve 22, 22′ for displacement relative to the sleeve;and a compression spring 25, 25′ which continually urges thecorresponding plunger 24, 24′ radially outward beyond the externalcylindrical surface 28 of intermediate portion 18. As FIG. 4A shows,plunger 24 is formed with a convex, spherical surface 26 located at aradial outer end of the plunger 24. Alternatively, as FIG. 4 b showsplunger 24′ may be a convex, sphere or ball retained in a concavespherical recess of sleeve 22′, or another suitable surface of thesleeve 22.

FIG. 5 shows that the sun gear 30 includes axially-directed internalspine teeth 32, an end chamfer 34 and helical gear teeth 36, whichengage planet pinions supported on the carrier (not shown) of aplanetary gear unit. The drive hub 10 is piloted into sun gear 30 due tocontact between chambers 13 and 34 and then sliding axially along thelength of the spline teeth 32 such that each of the plungers 24 islocated in a space between the spline teeth. Torque applied to the drivehub 10 is transmitted to the sun gear 30 due to contact between theplungers 24 and the face of an adjacent spline tooth 32.

In this illustrative embodiment, drive hub 10 has 21 plungers 24, eachlocated between two consecutive spline teeth 32 of sun gear 30. Eachplunger 24 applies circumferentially-directed force against one of thespline teeth 32 such that approximately 0.06 Nm of torque is developedbefore slippage occurs. With 21 operative ball plungers, torque having amagnitude of about 1.24 Nm is applied to the carrier assembly. Thisprovides sufficient torque to test the carrier assembly while providingmechanical over-torque protection to a load cell, which should notexceed 2 Nm.

Torque is applied to the drive hub 10 through a load cell, through whichthe application of torque is monitored. Torque is transmitted to drivehub 10 through hole 16.

Preferably the drive hub 10 is machined from preheated, cold rolledsteel bars conforming to ASTM A322, ASTM A331, ASTM A304, and is coatedwith titanium nitride for wear resistance.

The threaded insert is commercially available from Carr-Lane(CL-15-BP-1) and McMaster-Carr (3408A67).

In accordance with the provisions of the patent statutes, the preferredembodiment has been described. However, it should be noted that thealternate embodiments can be practiced otherwise than as specificallyillustrated and described.

The invention claimed is:
 1. An assembly, comprising: a sun gear thatincludes an external gear teeth and internal axial spline teeth; a drivehub including a first sleeve portion formed with lateral holes; aninsert, each insert including a sleeve located in one of the holes andsecured to the first sleeve portion, a plunger located in the sleeve,and a spring urging the plunger laterally outward toward engagement withthe spline teeth.
 2. The assembly of claim 1, wherein: each of the holesformed with an internal screw thread; and each of the inserts formedwith an external screw thread engaged with one of the internal screwthreads.
 3. The assembly of claim 1, wherein the drive hub furthercomprises: a second sleeve portion secured to the first sleeve portionand formed with a chamfer located at an axial end of the second sleeveportion.
 4. The assembly of claim 3 wherein the first and second sleeveportions each have the form of a right circular cylindrical sleeve. 5.The assembly of claim 1, wherein the plunger includes a convex sphericalsurface located at a lateral outer end.
 6. The assembly of claim 1,wherein: the sun gear further includes a first chamfer located at axialend of the spline teeth; and the drive hub includes a second chamferlocated at an axial end of the first sleeve portion for piloting thedrive hub axially into the spline teeth.
 7. An assembly, comprising: adrive hub including a first sleeve portion formed with lateral holes;inserts, each insert including a sleeve located in one of the holes andsecured to the first sleeve portion, a plunger located in the sleeve fordisplacement along the sleeve, and a spring urging the plunger laterallyoutward.
 8. The assembly of claim 7, wherein: each of the holes formedwith an internal screw thread; and each of the inserts formed with anexternal screw thread engaged with one of the internal screw threads. 9.The assembly of claim 7, wherein the drive hub further comprises: asecond sleeve portion secured to the first sleeve portion and formedwith a chamfer located at an axial end of the second sleeve portion. 10.The assembly of claim 9 wherein the first and second sleeve portionseach have the form of a right circular cylindrical sleeve.
 11. Theassembly of claim 7, wherein the plunger includes a convex sphericalsurface located at a lateral outer end.
 12. A method for forming atorsional drive connection, comprising: forming a sun gear that includesinternal axial spline teeth and a first chamfer located at axial end ofthe spline teeth; forming a drive hub having lateral holes and a secondchamfer located at an axial end of the drive hub; inserting a plungerinto each of the holes, the plunger protruding laterally past an outerradial surface of the drive hub; using the first and second chamfers topilot the drive hub into the sun gear such that each of the plungers islocated between consecutive spline teeth.
 13. A method of claim 12,further comprising: moving the drive hub axially into engagement withthe sun gear; transmitting torque from the drive hub to the sun gearthrough contact between the plungers and the spline teeth.